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Modulation Mapper. Scrambler. Layer Mapper. Precoder. Antenna Ports. CWs. Layers. Modulation Mapper. Scrambler. N t : Number of antennas. L : Number of layers. Q : Number of codewords. Proposed Transmission Framework. General transmission structure single-user MIMO (SU-MIMO) for DL.
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Modulation Mapper Scrambler Layer Mapper Precoder Antenna Ports CWs Layers Modulation Mapper Scrambler Nt: Number of antennas L: Number of layers Q: Number of codewords Proposed Transmission Framework • General transmission structure single-user MIMO (SU-MIMO)for DL • For any STC scheme, including • Spatial multiplexing (SM) • Transmit diversity (TxD) • Combined Now is FFS and needs to be determined for further evaluation!
Single Codeword (SCW) vs. Multiple Codeword (MCW) • SCW • Data block is coded and modulated into single coded block (Q= 1) • When rank of channel r = 1, SCW is used • MCW • Data block is segmented, coded and modulated separately into multiple coded sub-blocks (Q> 1) • For SU-MIMO, the maximum number of CWs per data block (or that can be received by UE) is determined by • Number of modulation & coding sets (MCSs) • Channel quality indicator (CQI) feedback overhead
Layer Mapping • In spatial multiplexing (or combined schemes), number of layers for MIMO channel is determined by • MIMO configuration • Channel state information (CSI), including spatial correlation • CQI feedback • In transmit diversity, number of layers is equal to number of transmit antennas • Number of CWs is constrained by number of layers and controlled through layering unit • To prevent performance loss from using higher number of MIMO layers than that can be supported by channel (Lr)
(b) Rank 2: CW 1 to Layers 1 & 2 (a) Rank 1: CW 1 to Layer 1 . . . Precoder . . . Precoder (c) Rank 3: CW 1 to Layers 1, 2 & 3 (d) Rank 4: CW 1 to Layers 1 to 4 . . . Precoder . . . Precoder Layer Mapping • CW-to-layer mapping for spatial multiplexing • SCW (Example: Q = 1, L 4)
(e) Rank 2: CW 1 to Layer 1 CW 2 to Layer 2 . . . Precoder (g) Rank 4: CW 1 to Layer 1 & 2 CW 2 to Layers 3 & 4 (f) Rank 3: CW 1 to Layer 1 CW 2 to Layers 2 & 3 . . . . . . Precoder Precoder Layer Mapping • CW-to-layer mapping for spatial multiplexing • MCW (Example: Q = 2, L 4)
Conclusion • Urgent parameters related to DL SU-MIMO • Maximum antenna configuration • Maximum number of layers (independent streams) for spatial multiplexing • Maximum number of CWs • Re-evaluate CW-to-layer mapping for spatial multiplexing in DL SU-MIMO
Text Proposal • Insert the following text into Physical Layer sub-sub-clause (IEEE C802.16m-08/003): -----------------------------------------------------------Start of Text Proposal----------------------------------------------------------- 11.1 High Level Principles for Downlink Single-User MIMO 11.1.1 Number of Codewords TBD 11.1.2Layer Mapping TBD ------------------------------------------------------------End of Text Proposal------------------------------------------------------------